The objective of this Fogarty International Research Collaboration Award (FIRCA) project is to elucidate structure-function relationships of calcium release channels (CRCs). In the past 5 years important advances have been achieved in terms of identifying functional domains of the channels and in understanding the role of the FK506 binding protein (FKBP12/12.6) in regulating RyR function. Significant new findings and preliminary data include: 1) FKBP12/12.6 stabilize RyR1 and RyR2 function; 2) identification of the binding site for FKBP12/12.6 on RyR1 and RyR2; 2) RyRs are physically bound to neighboring RyRs and 2 or more channels can exhibit "coupled gating" in planar lipid bilayers (believed to be important for controlling EC coupling). The proposed collaboration is between the laboratories of Dr. Andrew R. Marks (Columbia University College of Physicians & Surgeons, New York) and Dr. Karol Ondrias (Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Bratislava, Slovakia). The goal of this proposal is to extend the aims of the parent grant (R0l HL56180-07) which focuses on the molecular regulation of RyRs. The aims of this proposal are designed to take advantage of: 1) model systems for heterologous functional expression of RyR developed in Dr. Marks' laboratory; 2) the discovery of the phenomenon of coupled gating between individual RyR channels which resulted from the previous FIRCA award to the applicants; 3) extensive expertise in the use of planar lipid bilayers to study the single channel properties of calcium release channels in Dr. Ondrias' laboratory; 4) the opportunity to establish new technologies in the foreign laboratory based on studies of recombinant CRCs in planar lipid bilayers. Aim 1 proposes to characterize coupled gating between cardiac ryanodine receptors (RyR2) using single channel recordings in planar lipid bilayers. Aim 2 is to determine whether inositol 1,4,5-trisphosphate receptors (IP3Rs) exhibit coupled gating. Aim 3 is to characterize the gating function of lP3Rs channels that lack coupling domains. CRCs are required for many biological functions including T cell activation, muscle contraction, neurotransmitter release, cell growth and apoptosis. Pharmacologic manipulation, targeted at the regulation of these channels, could ultimately provide novel approaches to treating these and other diseases.